A direct comparison of long- and short-acting GLP-1 receptor agonists (taspoglutide once weekly and exenatide twice daily) on postprandial metabolism after 24 weeks of treatment

AIMS

T-emerge 2 was a randomized, open-label, 24-week trial comparing subcutaneous taspoglutide 10 mg weekly (Taspo10), taspoglutide 20 mg weekly (Taspo20; titrated after 4 weeks of Taspo10), with exenatide 10 mcg BID (Exe; after 4 weeks of Exe 5 mcg) in patients inadequately controlled on metformin, a thiazolidinedione, or both. T-emerge 2 showed that once-weekly Taspo provided better glycaemic control than Exe. This report focuses on a subset of T-emerge 2 participants undergoing a standardized liquid meal comparing Taspo to Exe, which has been previously shown to lower postprandial glucose.

METHODS

Meal tolerance tests (MTT) were performed at baseline and at week 24 in a subset of Taspo10, Taspo20 and Exe patients (n = 42, 39 and 67, respectively). Blood samples for glucose, insulin, glucagon and C-peptide were obtained before and after (30, 60, 90, 120 and 180 min) ingestion of a standardized liquid meal.

RESULTS

The 2-h postprandial, mean 0-3 h and iAUC0-3 h glucose during the MTT was reduced to a similar extent in all groups and the time profile of the postprandial glucose showed a similar pattern. Taspo10 and Taspo20, but not Exe, significantly increased insulin from baseline (both mean and iAUC0-3 h). Although changes from baseline in C-peptide were not significant within any treatment group, the mean change from baseline (both mean 0-3 h and iAUC0-3 h) was significantly increased in Taspo10 vs. Exe. Mean glucagon showed significant decreases in all groups.

CONCLUSION

Taspoglutide and Exe improved postprandial glucose tolerance to a similar extent but possibly with different intimate mechanisms.

Genetic disruption of SOD1 gene causes glucose intolerance and impairs β-cell function

Oxidative stress has been associated with insulin resistance and type 2 diabetes. However, it is not clear whether oxidative damage is a cause or a consequence of the metabolic abnormalities present in diabetic subjects. The goal of this study was to determine whether inducing oxidative damage through genetic ablation of superoxide dismutase 1 (SOD1) leads to abnormalities in glucose homeostasis. We studied SOD1-null mice and wild-type (WT) littermates. Glucose tolerance was evaluated with intraperitoneal glucose tolerance tests. Peripheral and hepatic insulin sensitivity was quantitated with the euglycemic-hyperinsulinemic clamp. β-Cell function was determined with the hyperglycemic clamp and morphometric analysis of pancreatic islets. Genetic ablation of SOD1 caused glucose intolerance, which was associated with reduced in vivo β-cell insulin secretion and decreased β-cell volume. Peripheral and hepatic insulin sensitivity were not significantly altered in SOD1-null mice. High-fat diet caused glucose intolerance in WT mice but did not further worsen the glucose intolerance observed in standard chow-fed SOD1-null mice. Our findings suggest that oxidative stress per se does not play a major role in the pathogenesis of insulin resistance and demonstrate that oxidative stress caused by SOD1 ablation leads to glucose intolerance secondary to β-cell dysfunction.

The fate of taspoglutide, a weekly GLP-1 receptor agonist, versus twice-daily exenatide for type 2 diabetes: the T-emerge 2 trial

OBJECTIVE

Taspoglutide is a long-acting glucagon-like peptide 1 receptor agonist developed for treatment of type 2 diabetes. The efficacy and safety of once-weekly taspoglutide was compared with twice-daily exenatide.

RESEARCH DESIGN AND METHODS

Overweight adults with inadequately controlled type 2 diabetes on metformin ± a thiazolidinedione were randomized to subcutaneous taspoglutide 10 mg weekly (n = 399), taspoglutide 20 mg weekly (n = 398), or exenatide 10 µg twice daily (n = 392) in an open-label, multicenter trial. The primary end point was change in HbA(1c) after 24 weeks.

RESULTS

Mean baseline HbA(1c) was 8.1%. Both doses of taspoglutide reduced HbA(1c) significantly more than exenatide (taspoglutide 10 mg: -1.24% [SE 0.09], difference -0.26, 95% CI -0.37 to -0.15, P < 0.0001; taspoglutide 20 mg: -1.31% [0.08], difference -0.33, -0.44 to -0.22, P < 0.0001; exenatide: -0.98% [0.08]). Both taspoglutide doses reduced fasting plasma glucose significantly more than exenatide. Taspoglutide reduced body weight (taspoglutide 10 mg, -1.6 kg; taspoglutide 20 mg, -2.3 kg) as did exenatide (-2.3 kg), which was greater than with taspoglutide 10 mg (P < 0.05). HbA(1c) and weight effects were maintained after 52 weeks. More adverse events with taspoglutide 10 and 20 mg than exenatide developed over time (nausea in 53, 59, and 35% and vomiting in 33, 37, and 16%, respectively). Allergic and injection-site reactions were more common with taspoglutide. Discontinuations were greater with taspoglutide. Antitaspoglutide antibodies were detected in 49% of patients.

CONCLUSIONS

Once-weekly taspoglutide demonstrated greater glycemic control than twice-daily exenatide with comparable weight loss, but with unacceptable levels of nausea/vomiting, injection-site reactions, and systemic allergic reactions.

β-Adrenergic Responsive Induction of Insulin Resistance in Liver of Aging Rats

INTRODUCTION. We previously demonstrated increases in β-adrenergic receptor (β-AR) density in rat liver, in association with increased β-AR-mediated stimulation of glucose output in rat hepatocytes, during senescent aging. We therefore hypothesized that pharmacologic β-adrenergic stimulation might induce insulin resistance and glucose output in liver of aging rats in vivo. METHODS. In this study, pancreatic clamps were performed on young adult (4-month-old) and senescent (24-month-old) Fischer 344 male rats by infusing somatostatin (3 μg/kg/min) at time 0 to inhibit insulin secretion, and then infusing insulin (1 mU/kg/min) to replace basal insulin concentrations. At time 0 rats also received either the β-AR agonist isoproterenol (100 ng/kg/min) or saline (control). After 120 min the insulin infusion rate was increased to 4 mU/kg/min for an additional 120 min. Tritiated glucose was infused throughout the study to measure glucose turnover rates. RESULTS AND CONCLUSION. The results of the pancreatic clamp studies demonstrated that under saline control conditions hepatic glucose production (HGP) was suppressed during hyperinsulinemia in both young and old rats, with a trend toward reduced insulin sensitivity in the older animals. Isoproterenol infusion impaired insulin-induced suppression of HGP in both age groups. The results suggest that β-AR stimulation by isoproterenol increases HGP and acutely induces hepatic insulin resistance in both young and old rats. A similar role for β-adrenergic-mediated hepatic insulin resistance in aging humans would suggest a novel therapeutic target for the treatment or prevention of glucose dysregulation and diabetes developing with advancing age.

Pioglitazone in the treatment of NASH: the role of adiponectin

BACKGROUND

Plasma adiponectin is decreased in NASH patients and the mechanism(s) for histological improvement during thiazolidinedione treatment remain(s) poorly understood.

AIM

To evaluate the relationship between changes in plasma adiponectin following pioglitazone treatment and metabolic/histological improvement.

METHODS

We measured in 47 NASH patients and 20 controls: (i) fasting glucose, insulin, FFA and adiponectin concentrations; (ii) hepatic fat content by magnetic resonance spectroscopy; and (iii) peripheral/hepatic insulin sensitivity (by double-tracer oral glucose tolerance test). Patients were then treated with pioglitazone (45 mg/day) or placebo and all measurements were repeated after 6 months.

RESULTS

Patients with NASH had decreased plasma adiponectin levels independent of the presence of obesity. Pioglitazone increased 2.3-fold plasma adiponectin and improved insulin resistance, glucose tolerance and glucose clearance, steatosis and necroinflammation (all P < 0.01-0.001 vs. placebo). In the pioglitazone group, plasma adiponectin was significantly associated (r = 0.52, P = 0.0001) with hepatic insulin sensitivity and with the change in both variables (r = 0.44, P = 0.03). Increase in adiponectin concentration was related also to histological improvement, in particular, to hepatic steatosis (r = -0.46, P = 0006) and necroinflammation (r = -0.56, P < 0.0001) but importantly also to fibrosis (r = -0.29, P = 0.03).

CONCLUSIONS

Adiponectin exerts an important metabolic role at the level of the liver, and its increase during pioglitazone treatment is critical to reverse insulin resistance and improve liver histology in NASH patients.